The present invention relates to manufacture of semiconductor wafers and more particularly to a method and system of polishing pad tensioning in a chemical mechanical polishing apparatus.
U.S. Pat. No. 6,103,628, assigned to the assignee of the present invention, describes a reverse linear chemical mechanical polisher, also referred to as bi-directional linear chemical mechanical polisher, that operates to use a bi-directional linear motion to perform chemical mechanical polishing. In use, a rotating wafer carrier within a polishing region holds the wafer being polished.
U.S. patent application Ser. No. 09/684,059, filed Oct. 6, 2000, which is a continuation-in-part of U.S. Pat. No. 6,103,628, describes various features of a reverse linear chemical mechanical polisher, including incrementally moving the polishing pad that is disposed between supply and receive spools.
While the inventions described in the above patent and application are advantageous, further novel refinements are described herein which provide for a more efficient drive system that creates the reverse linear (or bidirectional linear) motion.
The present invention offers many advantages, including the ability to efficiently produce reverse linear motion for a chemical mechanical polishing apparatus.
Another advantage of the present invention is to provide for the ability to efficiently produce bi-directional linear motion in a chemical mechanical polishing apparatus that also allows for the incremental movement of the polishing pad.
Another advantage of the present invention is the provision for a single casting that houses the polishing pad, including the supply spool, the receive spool, and pad path rollers.
The present invention provides the above advantages with a method and apparatus for producing bi-directional linear polishing that uses a flexible pad. In one aspect, a portion of the polishing pad is disposed under tension between a supply spool and a receive spool, with a motor providing the tension to either the supply spool or the receive spool and the other spool being locked during processing. If a new section of the polishing pad is needed, the same motor that provided the tension, if connected to the receive spool, is used to advance the polishing pad a determined amount. Further, during processing, a feedback mechanism is used to ensure that the tension of the polishing pad is consistently maintained.